Add progressive web app companion for cross-platform access

Vite + TypeScript PWA that mirrors the Android app's core features:
- Pre-processed shelter data (build-time UTM33N→WGS84 conversion)
- Leaflet map with shelter markers, user location, and offline tiles
- Canvas compass arrow (ported from DirectionArrowView.kt)
- IndexedDB shelter cache with 7-day staleness check
- Service worker with CacheFirst tiles and precached app shell
- i18n for en, nb, nn (ported from Android strings.xml)
- iOS/Android compass handling with low-pass filter
- Respects user map interaction (no auto-snap on pan/zoom)
- Build revision cache-breaker for reliable SW updates

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pwa/node_modules/babel-plugin-polyfill-corejs2/lib/helpers.js

@@ -0,0 +1,33 @@
+"use strict";
+
+exports.__esModule = true;
+exports.hasMinVersion = hasMinVersion;
+var _semver = _interopRequireDefault(require("semver"));
+function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
+function hasMinVersion(minVersion, runtimeVersion) {
+  // If the range is unavailable, we're running the script during Babel's
+  // build process, and we want to assume that all versions are satisfied so
+  // that the built output will include all definitions.
+  if (!runtimeVersion || !minVersion) return true;
+  runtimeVersion = String(runtimeVersion);
+
+  // semver.intersects() has some surprising behavior with comparing ranges
+  // with preprelease versions. We add '^' to ensure that we are always
+  // comparing ranges with ranges, which sidesteps this logic.
+  // For example:
+  //
+  //   semver.intersects(`<7.0.1`, "7.0.0-beta.0") // false - surprising
+  //   semver.intersects(`<7.0.1`, "^7.0.0-beta.0") // true - expected
+  //
+  // This is because the first falls back to
+  //
+  //   semver.satisfies("7.0.0-beta.0", `<7.0.1`) // false - surprising
+  //
+  // and this fails because a prerelease version can only satisfy a range
+  // if it is a prerelease within the same major/minor/patch range.
+  //
+  // Note: If this is found to have issues, please also revist the logic in
+  // babel-core's availableHelper() API.
+  if (_semver.default.valid(runtimeVersion)) runtimeVersion = `^${runtimeVersion}`;
+  return !_semver.default.intersects(`<${minVersion}`, runtimeVersion) && !_semver.default.intersects(`>=8.0.0`, runtimeVersion);
+}